1. Field of the Invention
The present invention relates to a gas turbine, a method of controlling air supply and a computer program product for controlling air supply.
2. Description of the Related Art
The gas turbine is operated by injecting high temperature gas generated by a combustor to a turbine. After the operation of the gas turbine is stopped, the high temperature gas stays in a combustor-accommodating chamber in which the combustor is accommodated, and a temperature difference is generated in an upper half and a lower half of the combustor-accommodating chamber. An upper side of the combustor-accommodating chamber having high temperature expands, and a lower side of the combustor-accommodating chamber having low temperature relatively contracts. Therefore, the combustor-accommodating chamber is deformed and a so-called cat back phenomenon is generated. To suppress the cat back phenomenon, Japanese Patent Application Laid-Open No. 2004-218569 discloses in its paragraph 0004 a technique (abbreviated as spin cooling, hereinafter) in which to reduce the temperature difference in a combustor-accommodating chamber 5, a turbine blade is rotated after the operation of the gas turbine is stopped to generate air current in the combustor-accommodating chamber, and temperature distribution in the combustor-accommodating chamber is reduced.
According to the technique disclosed in the above Japanese Patent Application, however, power for rotating the turbine blade after the operation of the gas turbine is stopped is necessary, and there is a problem that energy consumption for the power is high. The above Japanese Patent Application also discloses a technique to keep flowing purge air into the combustor-accommodating chamber, but this technique requires to continuously flow the purge air for a long time, and this technique is susceptible to improvement for reduction of energy consumption.